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8.0

Query tuning problem

Asked by chedgey in Oracle Database

Tags: query

I have recently upgraded a third party application from Oracle 8.1.6 to Oracle 9.2.0.7.0 and all is well apart from a couple of queries that are running poorly. The queries are based on a simple view and I am having problems seeing why the cost based optimiser is behaving as it is with it.

When i run the uderlying query of the view as a SQL statement it gives me a high cost but if I strip out the column list (keeping the rest of the query consitent) it behaves much better. Here are the plans from the 2 versions of the query:

Original Query
----------------
Explain Plan
Set STATEMENT_ID='GJC3'
For
SELECT IF_.R_OBJECT_ID,IF_.OBJECT_NAME
      ,IF_.R_OBJECT_TYPE,IF_.TITLE
      ,IF_.SUBJECT,IF_.A_APPLICATION_TYPE
      ,IF_.A_STATUS,IF_.R_CREATION_DATE,IF_.R_MODIFY_DATE,IF_.R_MODIFIER
      ,IF_.R_ACCESS_DATE,IF_.A_IS_HIDDEN,IF_.I_IS_DELETED,IF_.A_RETENTION_DATE
      ,IF_.A_ARCHIVE,IF_.A_COMPOUND_ARCHITECTURE,IF_.A_LINK_RESOLVED,IF_.I_REFERENCE_CNT
      ,IF_.I_HAS_FOLDER,IF_.R_LINK_CNT,IF_.R_LINK_HIGH_CNT,IF_.R_ASSEMBLED_FROM_ID
      ,IF_.R_FRZN_ASSEMBLY_CNT,IF_.R_HAS_FRZN_ASSEMBLY,IF_.I_CONTENTS_ID,IF_.A_CONTENT_TYPE,IF_.R_PAGE_CNT
      ,IF_.R_CONTENT_SIZE,IF_.A_FULL_TEXT,IF_.A_STORAGE_TYPE,IF_.I_CABINET_ID
      ,IF_.OWNER_NAME,IF_.OWNER_PERMIT,IF_.GROUP_NAME,IF_.GROUP_PERMIT,IF_.WORLD_PERMIT,IF_.I_ANTECEDENT_ID,IF_.I_CHRONICLE_ID,IF_.I_LATEST_FLAG,IF_.R_LOCK_OWNER,IF_.R_LOCK_DATE,IF_.R_LOCK_MACHINE,IF_.LOG_ENTRY,IF_.I_BRANCH_CNT,IF_.I_DIRECT_DSC,IF_.R_IMMUTABLE_FLAG,IF_.R_FROZEN_FLAG,IF_.R_HAS_EVENTS,IF_.ACL_DOMAIN,IF_.ACL_NAME,IF_.A_SPECIAL_APP,IF_.DOCUMENT_NUMBER,IF_.DOCUMENT_DATE,IF_.ISSUE_LEVEL
      ,IF_.I_IS_REFERENCE
      ,IF_.RESOLUTION_LABEL
      ,IF_.R_IS_VIRTUAL_DOC
      ,IF_.R_IS_PUBLIC
      ,IF_.R_CREATOR_NAME
      ,IF_.R_POLICY_ID
      ,IF_.R_RESUME_STATE
      ,IF_.R_CURRENT_STATE
      ,IF_.R_ALIAS_SET_ID
      ,IF_.I_IS_REPLICA
      ,IF_.A_CATEGORY
      ,IF_.LANGUAGE_CODE
      ,IF_.I_VSTAMP
      ,UY_.DCA_IDENTIFIER
      ,UY_.DCA_CURRENT_STATUS
      ,UY_.DCA_PROJECT
      ,UY_.DCA_DATE_OPENED
      ,UY_.DCA_DESCRIPTION
      ,UY_.DCA_FORMAL
      ,UY_.DCA_WORKFLOW_ID
      ,UY_.DCA_SUBMITTED
      ,UY_.DCA_DESTINATION
      ,UY_.DCA_PUBLISHING_INFO
      ,UY_.DCA_LOCKOWNER
      ,UY_.DCA_REJECTION_NOTES
      ,UY_.DCA_FINALISED_DATE
      ,UY_.DCA_FORMAL_START_DATE
      ,UY_.ACTIVE_REVIEWERS
  FROM LMREDMS.dm_sysobject_s IF_
      ,LMREDMS.lm_dca_s UY_
 WHERE IF_.R_OBJECT_ID=UY_.R_OBJECT_ID
/

Query Plan                                                                      
--------------------------------------------------------------------------------
1.33774 SELECT STATEMENT    GJC3 Cost=33774                                    
--2.1 HASH JOIN                                                                
  --3.1 TABLE ACCESS FULL LM_DCA_S                                              
  --3.2 TABLE ACCESS FULL DM_SYSOBJECT_S                                        


Column list removed
-----------------------
Explain Plan
Set STATEMENT_ID='GJC3'
For
SELECT IF_.R_OBJECT_ID
      ,UY_.R_OBJECT_ID
  FROM LMREDMS.dm_sysobject_s IF_
      ,LMREDMS.lm_dca_s UY_
 WHERE IF_.R_OBJECT_ID=UY_.R_OBJECT_ID
/
Query Plan                                                                      
--------------------------------------------------------------------------------
1.289 SELECT STATEMENT    GJC3 Cost=289                                        
--2.1 NESTED LOOPS                                                              
  --3.1 INDEX FAST FULL SCAN D_1F004421800001A1 UNIQUE                          
  --3.2 INDEX UNIQUE SCAN D_1F00442180000108 UNIQUE                            


Can anyone tell me why the first query with all the columns listed takes so much longer than the second. All tables are analyzed and the optimizer rule is set to "Choose. The DM_SYSOBJECTS_S table contains about 1,600,000 rows and the LM_DCA_S table about 33,000. Both tables have an index on the R_OBJECT_ID column

Thanks in advance

Chedgey
[+][-]09/18/06 06:57 AM, ID: 17543519Accepted Solution

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About this solution

Zone: Oracle Database
Tags: query
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Solution Provided By: johnsone
Participating Experts: 2
Solution Grade: C
 
[+][-]09/18/06 04:48 AM, ID: 17542534Assisted Solution

Assisted solutions are selected by the member who asked the question as a comment that contributed to their question's solution.

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[+][-]09/21/06 06:57 AM, ID: 17569115Author Comment

Often, when Experts are collaborating with members who have asked questions, they will request additional information about the problem. Askers respond with an author comment like this one.

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